Filterbank-based multicarrier (FBMC) communication systems are of increasing interest in the context of dynamic or shared spectrum access and inter-operator sharing. In these contexts, different communication systems can coexist in the same frequency band and an exclusive and contiguous usage of the frequency band for one communication system may not be realizable. Therefore, the receiver has to cope with interference from different users within its allocated frequency band and has to deal with a fragmented frequency spectrum.
Synchronization schemes for filterbank-based multicarrier systems are usually performed in the time-domain, where it is assumed that the multicarrier signals cover a contiguous bandwidth with no interfering signals.
However, time-domain based synchronization schemes suffer from several drawbacks. Time-domain based synchronization schemes may fail to synchronize if other users or interfering signals exhibit higher signal power than expected at the receiver. Furthermore, additional pre-filtering techniques of the time-domain signal may come at high implementation costs and may lead to distortion of the signals. Moreover, time-domain based synchronization schemes may be based on a large number of pilot symbols which may lead to a penalty in spectral efficiency of the communication system. Finally, implementation costs for time-domain based synchronization schemes may scale linearly with the number of users.
Synchronization schemes for filterbank-based multicarrier systems can also be performed in the frequency-domain.
In T. H. Stitz, T. Ihalainen, A. Viholainen, M. Renfors, “Pilot-Based Synchronization and Equalization in Filter Bank Multicarrier Communications,” EURASIP Journal on Advances in Signal Processing, vol. 2010, pp. 1-19, 2010, a pilot-based synchronization scheme in frequency-domain is presented. The presented synchronization scheme is based on a fixed pilot symbol arrangement of legacy systems. Furthermore, the presented synchronization scheme assumes coarsely pre-synchronization and suffers from a limited offset estimation range.
In T. H. Stitz, T. Ihalainen, M. Renfors, “Practical issues in frequency domain synchronization for filter bank based multicarrier transmission,” Communications, Control and Signal Processing, 2008, ISCCSP 2008, 3rd International Symposium, 2008, pp. 411-416, a preamble-based synchronization scheme in oversampled filterbank-based multicarrier systems is presented. The presented synchronization scheme is based on a long pilot symbol arrangement with boosted signal power and suffers from a limited offset estimation range.